Getter



Dec. 20, 1960 T. D. JAYNE 2,965,218

GETTER Filed Aug. 16, 1956 INVENTOR.

THEODORE DOUGLAS JAYNE ATTORNEYS GEITER Theodore D. Jayne, Painesville,Ohio, assignor to Rand Development Corporation, Cleveland, Ohio, acorporation of Ohio Filed Aug. 16, 1956, Ser. No. 604,390

3 Claims. (Cl. 206-.4)

This invention relates to improvements in a getter for improving thevacuum in an enclosed space, and to a method for maintaining a very highvacuum in an enclosing chamber surrounding a bottle of liquid gas suchas liquefied oxygen.

An object of the present invention is the provision of a unitary getterwhich combines within itself efiicient means for absorbing both oxygenand nitrogen, as well as hydrogen and other gases each time the getteris energized.

Another object of the present invention is to provide a getter which maybe completely sealed within the chamber where the high vacuum is to bemaintained with electrical leads to the outside and wherein there isconnected on the inside between the electrical leads a zirconiumfilament so spaced with respect to a titanium shield that whenelectricity is applied to the zirconium filament, that filament isheated to its efiicient range for absorbing oxygen and nitrogen and thetitanium shield is at such a distance from the filament that it in turnis heated to its most efiicient temperature for absorbing hydrogen fromthe vacuum space.

Another object of the present invention is to provide an efficient meansfor maintaining an almost perfect vacuum, of the order of one micron orless in a completely enclosed space, comprising the sealing of a getterwithin said space with electrical connections extending outside of saidspace, said getter including sufficient metal for absorbing the expectedgases within the vacuum chamber over a considerable period, so thatelectricity may be connected to the electrodes outside of said spaceintermittently from time to time for short periodsof time, at eachenergization removing the gases from the vacuum space to provide analmost perfect vacuum, and reusable a number of times so that theinstallation is good for a rather long total period.

Other objects and advantages of the present invention will be apparentfrom the accompanying drawings and description and the essentialfeatures will be set forth in the appended claims.

In the drawings,

Fig. l is a slightly. enlarged perspective view of my improved gettershowing oneembcdiment adapted to be sealed in the wall of a vacuumchamber;

Figs. 2 and 3 arefragmental. sectional views taken along similarlynumbered. lines of Fig. 1;

Fig. 4 is a view somewhat diagrammatic taken through a bottle for thestorage of liquid oxygen; while I Fig. 5 is a fragmental sectional viewsomewhatdiagrammatic showing a modification of the arrangement of Fig.4. f

. Liquid gases, such as liquid oxygen, with temperatures in the range of180 degrees Fahrenheit and lower, must be stored in vacuum jacketedcontainers. It is known that the adequate vacuum for storage of liquidgas is less than three microns of absolute pressure as measured on amercury gauge.- For storage of large quantities or for aircraft usewhere a pressure delivery ice system is used, metal containers arerequired. The' vacuum insulating space in this type of container issubject to continuing outgassing and to diffusion of gas through themetal as well as through microscopic holes in the welds required forfabrication of the container, Over a period of several months thiscauses a loss of vacuum and the resultant heat transfer to the storedcontents due to the lowered vacuum of the insulating chamber. This faultis particularly noticeable in five, eight and twenty liter oxygenconverter systems utilized by the United States Air Force.

I have chosen to illustrate the use of my improved getter in connectionwith such a portable vacuum bottle shown somewhat diagrammatically inFig. 4 and wherein the liquid oxygen container 10 is approximately fiveliters in capacity. This is surrounded by the vacuum chamber 11, whichis a gas tight chamber between the walls 10 and 12 and has approximatelyten liters capacity. This vacuum bottle is spheroidal in shape measuringapproximately 12 /2 inches by 10 inches outside dimensions and theaverage distance between the walls 10 and 12 is approximately of aninch. The walls 10 and 12 have been made of copper although morerecently they are made of stainless steel.

My improved getter, shown here, comprises a generally circular baseplate 13 of any suitable metal, such as stainless steel or a metalhaving the trade-name Kovar, into which are sealed two filamentsupporting electrodes 1.4, diametrically opposite each other, and twoshield supporting posts 15 also diametrically opposite each other andpreferably about degrees spaced from the electrodes 14. The electrodes14 and the posts 15 are supported in and insulated from the base plate13 by gobs of glass 16. The electrodes 14 and the posts 15 are made of ametal having the trade-name Kovar which is a known metal having the samecoefficient of expansion as glass and having approximately the analysisof 20 percent nickel, 17 percent cobalt, 0.2 percent manganese and thebalance iron. Between the inner ends of the electrodes 14 iselectrically connected a zirconium wire filament 17 which, in thepresent embodiment, comprises two zirconium wires about No. 25 B. and S.gauge, which wires are twisted together and then wound in a helical formwith the axis of the helix approximately parallel to the base plate 13and slightly more than of an inch spaced from the base plate 13. Thisgives approximately 1 gram of zirconium in this filament.

Spaced from the zirconium filament and generally parallel to it is atitanium shield 18 of sheet metal form. This shield is so placed withrespect to the filament that when the filament is heated to atemperature of approximately 1200 degrees F. to 1600 degrees F., itwarms the titanium shield to between 600 degrees F. to 800 degrees F. Atthese temperatures the zirconium filament is very active in picking upand reacting with oxygen and nitrogen, while the titanium shield isactive in picking up and holding hydrogen. Other gases such as carbondioxide are also absorbed by my improved getter. The titanium shieldshown here completely surrounds the filament 17 along almost its entirelength but with the ends of the shield open for the easy access of gasesto the interior of the shield. In the form shown here, the shield 18 isplaced on both sides of the filament 17 (although it could be on oneside only (and is about 9' inch wide, parallel to the axis of thefilament, and approximately /2 inch long opposite the filament, withflange portions 18a bent toward each other and then provided with ears18b extending laterally away from the filament and approximately in theplane of the axis of the filament. These ears 18b are secured firmly tothe posts 15. The spacing between the posts 15, in this embodiment, isapproximately /a inch and the electrodes 14 are similarly 3 spaced.Referring to Fig. 2, the diameter across the helix of the filament 17 isapproximately inch and the dimension between the two fiat portions ofthe shield 18 is approximately /2 inch. This leaves approximately inchbetween the base 13 and the titanium shield 18" which is adjacentthereto. Preferably, but not neces-- sarily, the metal of shield 18nearest plate 13 is bent. into a projection 18c opposite each electrode14, these projec-- tions 18c preventing tilting of the titanium shieldon its supporting posts- 15. 7

Referring to Figs. 1 to 4 inclusive, the base plate 13 has a continuousannular flange 13a around its periphery and this flange is suitablysecured as by solder around the edges of a suitable circular opening inthe wall 12 so that the getter is within the vacuum space 11 and theelectrodes 14 extend outside of this space as seen in Fig. 4, and thebase plate completely seals the opening in wall 12.

The other details of Fig. 4 have no connection with the presentinvention but illustrate a common construction of one of these vacuumbottles wherein the bottle is supported by a plurality of wires 19 fromthe wall 12, and suitable lines of communication with the bottle areprovided such as the vent line 20, closed by a valve 21, a gauge line 22closed by a gauge or plug at 23, and an oxygen outlet line 24 closed bya control valve 25. These lines of communication are showndiagrammatically, whereas in the actual bottle, these lines areapproximately 20 inches long to reduce the conduction of heat and theyare formed of wrought Inconel approximately 0.005 inch thick which is avery poor conductor of heat and comprises approximately 80 percentnickel, 13 percent chromium and 6 percent iron.

The use of my invention should now be apparent. With the getter in theposition of Fig. 4, but without the protective cover 26, a source ofeither alternating or direct current (diagrammatically illustrated at'29) is connected across the electrodes 14 so that between 30 and 4-0watts of current at 8 or 10 volts, and drawingabout 3 or 4 amperes, isapplied between the electrodes 14 to heat the zirconium filamentdirectly and to heat the titanium shield indirectly as mentioned above.By means of a controlled air leak, I have admitted about 100 microns,mercury gauge, of air to the chamber 11 and energization of my improvedgetter for about fifteen minutes has reduced this to approximately 1micron of mercury gauge pressure. When the chamber 11 is outgassed, theelectrical source 29 is disconnected. By a similar procedure, I haveremoved a calculated 1000 micron liters of a gaseous mixture consistingof oxygen, nitrogen and hydrogen and repeated this action as many asseven times usingthe same getter. When it is considered that it normallytakes a period of several'months to cause any great loss of vacuumwithin the chamber 11, it will be seen that my invention will maintainthe insulating value of the vacuum chamber over a long period of time.When the getter is used up, it is only necessary to unseal the flange13a, place a new getter in the same position and re-evacuate thecontainer. In normal use, while the electrical source is disconnected, aprotective cover 26 is sealed over the electrodes 14 and the posts 15 inthe position shown in Fig. '4 by-nieans of a solder seal aroundtheedges.

In the modification shown in Fig. 5, the getter is constructed in such away as to keep the heat away fromthe oxygen bottle. Here the bottle isshown diagrammatically at 10' with a vacuum chamber 11 between thebottle and the outer wall 12'. Secured'to a suitable opening in the wall12 is a small closed container 27 which is sealed as by solder atthecontinuous flange 27a 7 to the wall 12'- around the opening 28.Supported within the container 27 between the electrodes 14' is azirconium filament 17', these parts being constructed exactly like thosepreviously described except that this permits the construction of alonger filament if desired. Spaced from the filament is a titaniumshield 18 which is supported on posts, not shown, analogous to the posts15 of the first described form. It is obvious that the operation of thisform of the invention is exactly like that first described because thegases in the chamber 11' have free access to the interior of thecontainer 27 through the opening 28 for the purpose of the getteraction.

When heat is applied to the filament 17 or 17, in either form of myinvention, but more particularly in connection with the first describedform involving the filament 17, oxygen which may be occluded in theinner shell 10 due to seepage, is to some extent released in the space11 between the shells 10 and 12 and is outgassed by my improved getter.

What is claimed is:

1. A unitary getter comprising a base plate, two spaced electrodesextending through said plate and sealed and electrically insulatedthere, a zirconium filament connected to and supported between saidelectrodes on one side of said plate and spaced from said plate, and atitanium shield mounted on said base plate on said one side thereof andspaced from said filament in position to be heated to the range of 600degrees Fahrenheit to 800 degrees Fahrenheit for outgassing hydrogenwhen said filament is heated to the range of 1200 degrees Fahrenheit to1600 degrees Fahrenheit for outgassing oxygen and nitrogen.

2. A unitary getter as defined in claim 1 wherein the amounts ofzirconium and titanium are sufficient to outgas a vacuum chambersurrounding said getter a plurality of times, whereby electrical energymay be connected to said electrodes from time to time to carry out aplurality of such outgassing operations utilizing a single getter.

3. The method of maintaining a high vacuum in a portable vacuum bottlehaving a vacuum chamber surrounding, a gas-tight storage chamber andhaving zirconium and titanium spaced close to and electrically insulatedfrom each other on a frame mounted inside said vacuum chamber with anelectrical heating circuit connected to said zirconium and extending toelectrodes out side said bottle; comprising the steps of connecting asource of electricity to said electrodes, heating said zirconium to atemperature at which it effectively outgasses oxygen and nitrogen fromsaid chamber and at the same time and at the said temperature thezirconium heats thetit'anium by transmitted heat to a temperature atwhich it effectively outgasses hydrogen from said-chamber, and thendisconnecting said electrical source when said outgassing is completed.

Germany July 5, 1924

